Hi Jeroen, and thanks for your reply.
This is the way we've currently implemented it, but the reason
I ask this is because of another line in the RFC, concerning
what happends when Timer C pops, chapter 16.8.
"If the client transaction has not received a provisional response, "
"the proxy MUST behave as if the transaction received a 408 "
"(Request Timeout) response.""
Now if I restart timer C for every new txn, and the above rule is
talking about not receiving any provisionals, then the transaction
should timeout(timer B or F) long before timer C is ever reached!
So unless we change T1 so that T1*64 is larger than the minimum of
3 minutes for Timer C, the above scenario should be impossible, since
timer C couldnt pop for a txn, since the txn has failed long before
not receiving any provisionals.
So I was simply a bit confused that the rfc would define rules that
in normal conditions wouldnt happend.
Regards
Taisto
Jeroen van Bemmel wrote:
> Hi Taisto,
>
>
> Timer C simply makes sure that things end eventually. If it takes too
> long, the UAC can CANCEL the process at any time. Each INVITE client
> transaction has its own timer C associated with it ("Timer C MUST be set
> for each client transaction when an INVITE request is proxied"). So a
> series of attempts trying a list of IP addresses from DNS (as you
> describe) would start a timer C for each.
>
>
> Regards,
>
>
> Jeroen
>
>
> ----- Original Message -----
> From: "Taisto Qvist" <[EMAIL PROTECTED]>
> To: <[email protected]>
> Sent: Wednesday, September 07, 2005 8:17 AM
> Subject: [Sip-implementors] restarting timer c on failures
>
>
>
>> Hi folks,
>>
>>
>> The rfc says to restart timer C on every provisional response
>> received, but what about the failures according to rfc3263.
>>
>> Chapter 4.3 says that on fatal transport error, or reception of a
>> 503,
>> or txntimeout w/o any provisionals, one should create a new txn and
>> send the request to the next server selected from the DNS-data
>> available.
>>
>> Do I update Timer C, when I create this new txn?
>> If I do, this could keep a proxy going for a very long time, if a lot
>> of the servers dns is pointing to, answer very slowly with 503s. Or
>> just a lot of consequtive transaction timeouts to each server in the
>> DNS-list.
>>
>>
>> Naturally it would require a big list of choices in the DNS, since
>> txns timeout after normally 32s, but I always saw the timer C as a
>> protection for making sure the proxy doesnt keep trying to long, so I
>> wouldnt want to restart it in these cases.
>>
>> Regards
>> Taisto Qvist
>> IP-Solutions AB
>>
>>
>> _______________________________________________
>> Sip-implementors mailing list
>> [email protected]
>> http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
>>
>
>
----
Taisto Qvist, IP-Solutions
Mobile: +46-708-88 02 63
"We are Pentium of Borg. Division is futile, You will be approximated"
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